Shingles intended for use in such applications as roofing and siding building materials have developed so that most commonly available shingle products now have a self-sealing adhesive layer or strip located upon a major surface of each shingle product. The adhesive or sealant which is placed upon the shingle during the manufacturing process is temperature sensitive and the sealant will activate when a specified threshold temperature is met. The threshold or activation temperature for the sealant can be selected to closely correlate with the expected ambient temperature of the specific geographical area in which the shingles are expected to be used. Usually the activation temperature will be selected to be from 20.degree.-60.degree. F. higher than the expected ambient temperature. When the shingles are applied during building construction the shingle will heat up as a result of solar heat absorption and activate the adhesive. The weight of the shingles will then seal the shingles together.
Problems have been encountered in packaging such self-sealing shingles in that the shingles are often left outdoors at a construction site, or a shingle manufacturer's or retailer's storage yard. These shingles will often be exposed to solar heat ambient temperatures which may activate the sealant causing the shingles to adhere to each other. Solar heat, if not deflected from the shingles, will be absorbed by the shingle products causing the bundle of shingles to reach a temperature substantially higher than ambient. If the temperature within the bundle reaches the tab sealant activation level, the sealant will become tacky and the shingles, stacked upon each other, will adhere to one another. Thus problems are created when the shingles are stored outdoors prior to use in construction.
There are specific packaging efforts which have been directed at solving this problem of self-sealing adhesion during shingle storage. For instance, U.S. Pat. No. 3,138,251 offers a solution to the problem through the use of a light cardboard-type wrapper which is folded over the bottom, sides and ends of the bundle of shingles. The wrapper ends are folded upon themselves and mated with the uppermost shingle in the bundle to cover a substantial portion of the head and butt portions of the shingles and create a gap between the folded ends. As the shingles are stacked, the adhesive strips are in approximate alignment adjacent the area of the gap thereby separating the adhesive portions of each shingle from the other shingles resting upon it. This type of packaging, however, has proven to be costly and time consuming in its application.
A more commonly accepted method for wrapping shingle bundles is to cover the bundles with a paper wrapper. This type of wrapper, while offering brief insulating properties from exposure to solar heat, often fails to maintain the interior temperature of a bundle of shingles at a sufficiently low temperature to avoid activating the self-sealing adhesive. A release paper or film is commonly placed over the sealant strips when the shingles are stacked in a bundle. Even though a release paper is used, under certain storage conditions the shingles will still adhere to each other in the bundle.
Another problem with high temperatures due to solar heating under storage conditions is staining of the lighter colors of shingles, particularly the white shingles. It may be that the hot temperatures cause some of the oils to seep out from the base asphalt of the shingle. Prevention of extremely hot temperatures from solar loading will help alleviate this staining problem.
Recent attempts to enhance the packaging of shingle bundles have focused on the use of polyethylene films as packaging material. It is known that white polyethylene film and clear polyethylene film have been used. However, these films have shown no success in reducing the interior heat of the shingle bundle. In fact, tests have shown that both white and clear wrappers actually increase the interior heat of a bundle when compared to a paper wrapper.
Therefore, it is an object of this invention to facilitate ease of packaging of shingle bundles and pallet loads of shingle bundles.
It is a further object of this invention to package shingle bundles and pallet loads of shingle bundles in such a manner that the adhesive portions of the self-sealing shingles are maintained at a temperature which will be low enough so as not to cause the individual shingles to adhere to one another, even when exposed to solar heat.